The ability to weld onto in-service pipelines such as natural gas pipelines in which gas is actually already flowing. This makes it possible to add another section of a pipeline (hot tap branch connections) and to enable the installation of repair sleeves without interrupting the flow of gas (except for a few hours). While there are economic benefits to this practice, certain issues must be addressed to ensure that public, environmental, and worker safety is maintained both during and after welding and to ensure that the flow is indeed not interrupted for more than a number of hours and not days. The practice of welding onto in-service pipelines (hot tapping) is not uncommon.